Vehicle bumper structures may include internal reinforcing members formed from plastic materials, such as glass-filled polymers, which may have relatively little resilience and impact resistance. Reinforcing members formed from such materials may crack after minimal deformation, for example, due to a bumper impact event. Such cracks may propagate until a substantial portion of the bumper reinforcement separates from another portion of the reinforcement. In addition, since the bumper reinforcement may be enclosed within an outer shell, a user may be unaware that the bumper has been damaged, or of the extent of the damage.